ABSTRACT
This study extends the capability for directing cell behavior using PEG-based hydrogels in tissue-engineering applications to include control over the spatial distribution of the adhesive peptide, RGDS. A continuous linear gradient was formed by simultaneously using a gradient maker to combine precursor solutions and using photopolymerization to lock the RGDS gradient in place. Hydrogels containing entrapped gradients of bovine serum albumin (BSA) were characterized using Coomassie brilliant blue stain, which indicated that BSA concentration increases along the hydrogel's length and that the steepness of the gradient's slope can be varied by changing the relative BSA concentrations in the precursor solutions. Human dermal fibroblasts responded to covalently immobilized RGDS gradients by changing their morphology to align in the direction of increasing RGDS concentration. After 24 h, approximately 46% of fibroblasts were aligned with the RGDS-gradient axis. This proportion of cells further increased to approximately 53% (p < 0.05) and approximately 58% after 48 and 96 h, respectively. Also, fibroblasts migrated differentially depending on the concentration of RGDS. Fibroblasts migrated approximately 48% further going up the concentration gradient (0 to 6 micromol/ml PEG-RGDS) than going down the concentration gradient. Migration up the concentration gradient was also approximately 33% greater than migration on control surfaces with a constant concentration of RGDS (2 micromol/ml), while migration down the gradient was reduced approximately 12% relative to the control surface. In addition, directed migration was further enhanced by increasing the RGDS gradient's slope. This hydrogel system is expected to be useful for directing cell migration to enhance the formation of engineered tissues.
Subject(s)
Cell Movement/drug effects , Hydrogels/chemistry , Oligopeptides/pharmacology , Platelet Aggregation Inhibitors/pharmacology , Cells, Cultured , Fibroblasts/drug effects , Humans , Oligopeptides/administration & dosage , Oligopeptides/chemistry , Platelet Aggregation Inhibitors/administration & dosage , Platelet Aggregation Inhibitors/chemistry , Serum Albumin, Bovine/chemistry , Surface PropertiesABSTRACT
Basic fibroblast growth factor (bFGF) was immobilized to hydrogel scaffolds with retention of mitogenic and chemotactic activity. The bFGF was functionalized in order to incorporate it covalently within polyethylene glycol (PEG) hydrogel scaffolds by reaction with acryloyl-PEG-NHS. Hydrogels were formed by exposing aqueous solutions of PEG diacrylate, acryloyl-PEG-RGDS, and acryloyl-PEG-bFGF to long-wavelength ultraviolet light in the presence of a photoinitiator. These bFGF-modified hydrogels with RGD adhesion sites were evaluated for their effect on vascular smooth muscle cell (SMC) behavior, increasing SMC proliferation by approximately 41% and migration by approximately 15%. A covalently immobilized bFGF gradient was formed using a gradient maker to pour the hydrogel precursor solutions and then photopolymerizing to lock in the concentration gradient. Silver staining was used to detect the bFGF gradient, which increased linearly along the hydrogel's length. Cells were observed to align on hydrogels modified with a bFGF gradient in the direction of increasing tethered bFGF concentration as early as 24 h after seeding. SMCs also migrated differentially, up the concentration gradient, on bFGF-gradient hydrogels compared to control hydrogels with and without a constant bFGF concentration. These hydrogel scaffolds may be useful for studying protein gradient effects on cell behavior and for directing cell migration in tissue-engineering applications.
